1. Field of Invention
The present invention relates to the transmission of data in a radio telephone network.
2. Prior Art
An example of a radio telephone network, in this case a conventional digital cellular network, is shown in FIG. 1 A. The network comprises a number of Base Station Controllers (BSC), each of which controls a number of Base Transceiver Stations (BTS). The BTSs are connected via radio communications channels with one or more mobile stations (MS). A BSC and the fixed or base stations (BS) with which it is connected form a Base Station Subsystem (BSS). The BSCs are connected to Mobile Switching Centers (MSC) via digital trunk lines which control the Base Station Subsystems. The MSCs route communication traffic from the mobile stations to a general Public Service Telephone Network (PSTN) or to private networks, such as Local Area Networks (LAN). A Base Station Controller may also be physically located at a Mobile Switching Center. The service range of a base or fixed station defines and forms a "cell", and a mobile station within the service range is typically served by that BS. A mobile station is able to move from one cell to another and roam from under the control of one Base Station Controller to be under the control of another Controller without losing a connection to the radio telephone network.
In known cellular networks, data information can be transmitted between the home network of a mobile station and a terminal or destination network. The terminal network can include a home network, another network of the same system, a fixed telephone network, or a data network. The network services typically include synchronous and asynchronous circuit-switched data transfer from the cellular network to the external telephone network PSTN, to a circuit-switched data network or an ISDN network. Suggestions have also been made regarding implementing asynchronous packet switching to an external packet switched data network.
As shown in FIG. 1A, data transmitted by a mobile station (MS) is received by a BTS under the control of a BSC and enters a data Inter Working Functions unit, IWF, associated with the Mobile Switching Center (MSC), and from there passes, via a modem, to the Center. From the Center the data is further transmitted, e.g., via the PSTN, to a target means or target data network, such as a remotely located private LAN network. The transition network is thus the general telephone network.
A typical method of data transmission between networks and also within a network is circuit switching, in which a transfer channel is established for the transfer of data. However, establishing a channel is a time-consuming operation and requires a lot of signalling, such as the sending of a control channel request and the assignment of a channel, authentication checks, installation of an encrypting mode and others, before the channel is set up for transferring data information. Further, circuit switching, when applied for data transfer, is uneconomical since the transfer needs a wide frequency band. Also, a user is charged for channel use irrespective of whether data is transmitted or not, because in a circuit-switched network the channel has to be maintained until all data information has been transmitted, which, considering the capacity, is uneconomical. The user is usually charged based on the length of the reserved connection time in the circuit-switched network, so that the user is obliged to pay for a significant amount of "nil" time since the time used for the actual data transfer is a minor part of the total connection time. Typically, cellular networks have primarily been optimized for speech transfer, and for that purpose, circuit-switched signal transfer is appropriate.
In a digital cellular network, such as in the European GSM network and in the American network operating under the Electronic Industries Association/Telecommunication Industry Association (EIA/TIA) standards, it has been suggested that data communication be done in packets, as so-called packet data, e.g., as disclosed in U.S. Pat. No. 4,887,265 to K. A. Felix. This patent describes a system in which several mobile stations send packet data to one base station using the same channel. When the Base Station Controller receives an assignment request for a data channel from a mobile station, it transmits a channel assignment to that mobile station, whereby the mobile station moves on that data channel. The same channel is also available for use for all other mobile stations within the range of that cell. With this system a request, a channel assignment, and transfer on a channel require a considerable amount of signalling. Handover of a data connection from one base station to another is also possible in this system, and a permanent channel is provided for packet transfer, being constantly available, irrespective of a momentary need.
Problem to be Solved:
It will be seen that a considerable amount of signalling and extensive channel use time are generally required for data transmission in existing radio telephone systems.
Objects:
It is accordingly an object of the present invention to provide a radio telephone system wherein a mobile station and a fixed station store respective parameters for setting up a data communication channel in the form of a virtual data communication channel between them, which expedites the establishment of a real data communication channel.
It is another object of the invention to provide a method of transmitting data in a radio telephone network using the storing of a parameter of a mobile station for setting up a data communication channel at a fixed station, and the storing of a parameter of the fixed station for setting up a data communication channel at the mobile station, whereby a virtual data communication channel is formed between the mobile station and the fixed station to expedite the establishment of a real data communication channel.
It is a further object of the invention to provide a radio telephone that is adapted to store a parameter for setting up a communication channel of a fixed station for forming a virtual data communication channel with the fixed station thereby expediting establishment of a real data communication channel.